Potato Review

24 POTATO REVIEW JANUARY 2022 TUBER CARE B Y spring, potato seed has spent a long time in store – at considerable cost – to keep it in good condition until planting. The final danger to seed health ahead of planting is field pathogens like Rhizoctonia solani, which can have a damaging impact on marketable yield in progeny grown for all markets, including seed, ware, and processing. To avoid falling at this last hurdle, now is the time for seed buying customers to assess Rhizoctonia risk and ensure liquid treatment is applied before planting where necessary. Now – January – is also the last opportunity to treat for storage diseases like dry rot, gangrene, skin spot and silver scurf if the stock is still to be graded. Holding phase While the optimum window for these treatments has now passed, seed care expert Paul Overton says there may be value in applying products like Gavel Protect seed health right up to planting In the third and final article of our series looking at seed health, Potato Review gets some advice on minimising disease risk in the final stages of a seed tuber’s storage period in the run up to planting. at this late stage in some situations. Most seed crops are harvested into boxes, and some producers then load boxes into store straight away for cooling and drying and use temperature control and good ventilation to reduce risk of disease development. If first grading is scheduled for January there is the potential to cause fresh physical damage, heightening the risk of disease ingress, which can then develop in February/ March “holding phase” ahead of delivery. Paul says Gavel application doesn’t come at a huge cost and treating high-risk varieties before grading will help maximise saleable seed and the producer’s profit will be maximised. He adds that seed lots destined for export may also require treatment at this stage and due to the transport and shipping problems experienced globally, the need could be even more pressing. “We have been used to everything arriving on time over the years, but the world has changed over the last 18 months and product could be sat on lorries or in containers much longer than before. “This may allow disease to take hold during transit and compromise quality.” Pre-planting For those that have already managed storage pathogens, thoughts now turn to managing the impact of Rhizoctonia solani, a seed- and soil-borne disease that has a significant impact on crop quality. Kyran Maloney of SAC Consulting says that growers should be performing risk assessments as soon as possible to work out how the disease will be managed ahead of the new season, whether for certified or home-saved seed. Visual inspections of seed for signs of black scurf – the sclerotia that form on the surface of the potato and infect the following crop – should be carried out. Field history of where the seed will be planted is also a major factor in infection risk. Whilst not popular yet, there is also the option of sending tubers away to be tested at a plant clinic and having soil analysed for the presence of the pathogen to help avoid any nasty surprises post planting. All seed tuber treatments can cause a slight delay in emergence, but crops quickly catch up and benefits far outweigh the risks where Rhizoctonia is present, according to SAC Consulting trials.

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